Polyarylene sulfide resins (hereinafter sometimes abbreviated as “PAS resin”), the representative of which is a polyphenylene sulfide resin (hereinafter sometimes abbreviated as “PPS resin”), are excellent in heat resistance, chemical resistance and the like and widely utilized for applications such as electric/electronic parts, automotive parts, water heater parts, fibers and films.
A polyphenylene sulfide resin is conventionally manufactured by solution polymerization in which p-dichlorobenzene, and sodium sulfide, or sodium hydrosulfide and sodium hydroxide are used as raw materials to polymerize in an organic polar solvent (e.g., see Patent Literatures 1, 2). Polyphenylene sulfide resins which are currently commercially available are generally produced by this method.
However, since dichlorobenzene is used as a monomer in the method, the concentration of halogen remaining in the resin after synthesis tends to be high and it is necessary to perform polymerization reaction under a severe environment of high temperature and high pressure/strong alkaline, which requires to use a polymerization vessel in which the wetted part is made of titanium, chromium or zirconium, which is expensive and hard-to-process.
Accordingly is known a method for manufacturing a polyarylene sulfide resin under moderate polymerization conditions without using dichlorobenzene as a polymerizing monomer. For example, Patent Literature 3 discloses a solvent-soluble poly(arylenesulfonium salt) as a precursor for synthesizing a polyarylene sulfide resin. A poly(arylenesulfonium salt) is manufactured by a method in which a sulfoxide having one sulfinyl group (hereinafter sometimes referred to as “monofunctional sulfoxide”) such as methyl phenyl sulfoxide is homopolymerized under the presence of an acid (e.g., Patent Literature 3).